Twins aren’t that unusual. Quadruplets are rather less likely. And octuplets always make the news. In the world of ship-building, they are exceptionally rare.

So there was considerable surprise in cruise line circles when, between 1998 and 2001, Renaissance Cruises built and launched no fewer than eight identical sisters, rather unimaginatively christened R1, R2 and so on right up to R8.

In an era of ever-larger liners, these sisters were refreshingly different: just over 30,000 tonnes, carrying a little more than 650 passengers, mostly in balcony cabins. From the outside, they were well-proportioned and bluff. On the inside, each sister had an identical décor of rich panelling, brass wall lights, oriental rugs and traditional art that gave them the intimate allure of an English country house hotel.

For lovers of small-ship ambience, it seemed as if their eight ships had come in.

Unfortunately though, Renaissance made two gigantic errors. First, they proudly declared themselves the world’s first totally non-smoking cruise-line. Secondly, they preferred to sell their cruises direct, therefore alienating the massively powerful US Travel Agency Industry, traditionally the source of some 90% of all cruise bookings stateside.

The result of this daring double whammy was as simple as it was inevitable. Within two years, Renaissance Cruises was bankrupt and its sparkling new fleet in the hands of creditors.

Since then the eight sisters, like evacuees, have gone their separate ways. Now, by a curious quirk of fate, they find themselves competing with one another.

Three were acquired by Oceania Cruises. Renamed Insignia, Regatta and Nautica they underwent the most elaborate and extensive upgrades of the eight. Synthetic decking was replaced throughout the open decks with glowing teak. Outdoor cabanas were erected for private al fresco pampering. And ceiling fans were installed around the sheltered decks poolside. Oceania has very successfully occupied the gap between deluxe lines like Crystal and Regent and the premium class ships of Holland America and Celebrity, and established a well-earned reputation for some of the finest food at sea. Its lengthy port-intensive itineraries and casual style have made this the cruise line of choice for those who choose their cruise above all for the destination and shoreside experience.

Two more of the sisters were acquired by Royal Caribbean last year and initially transferred to that company’s Celebrity Cruise fleet. However, a sudden (and some would say hurried) volte-face saw them being diverted to a new premium/deluxe company called Azamara Cruises.

Azamara is a coined name meant to suggest the azure of the seas: and the ships have been imaginatively renamed Azamara Quest and Azamara Journey. To differentiate them from Oceania, Azamara has decided to offer some extra perks. For instance, there is butler service in all staterooms (a privilege normally reserved for only the top suites) and niceties like fresh flowers in all rooms. Complimentary dining in the a la carte restaurants is offered to all guests.

Azamara is so new that one of its ships has yet to enter service at the time of writing: initial reports suggest that there are teething problems still to sort out so perhaps the best advice about the fledgling company ought to be “Watch This Space”.

Perhaps the most surprising purchaser of the ships was Princess Cruises. For years now, they have followed the inevitable trend amongst leading cruise lines and built ever bigger ships with more of everything: more balcony cabins, more atria, more pools and – inevitably – more passengers. So the industry was a little surprised when Princess bought the three remaining, diminutive sisters.

But it seems as though Princess may actually have performed a master-stroke. Having divested themselves of intensely popular smaller ships like the original Island Princess and Pacific Princess (the original “Love Boats”) they found that there was a significant minority of passengers who genuinely missed the smaller scale ships.

So when they acquired the three ex-Renaissance sisters, they wisely decided not to change much about them at all. Instead they use the trio as a more adventurous version of their mainstream product.

I sailed from Athens to Barcelona this summer on Royal, and was pleasantly and unexpectedly surprised. The ship herself has changed little since her days with Renaissance (and then as Minerva II for Swan Hellenic), and she offers a sophisticated but understated shipboard experience I can best describe as ‘Princess lite’.

But the greatest thing about Royal Princess and all her seven sisters, regardless of whom they are now sailing for, is quite simply their intimate size. With only six hundred guests to accommodate, service is highly personal, the food better and the social environment far more convivial than any larger ships can offer.

If you want a cruise where your cabin is within easy reach of everything, where the crew remember your name and your preferences and where ports off the beaten track are the rule rather than the exception, you really couldn’t do better than sample one of this delightful octet of liners.